Apparatus for producing porous or spongy articles of rubber or rubberlike materials



March 16, 1943. J, ALALAY 2,314,176

- APPARATUS FOR PRODUCI POROUS OR SPONGY ARTICLES 0F RUBBER OR RUBBER LIKE MATERIALS Filed July 1, 1941 Patented Mar. 16,- 1943 UNITED STAT (APPARATUS FOR PRODI JCING POROUS OR 8 OF RUBBER R RUB- BERLIKE MATERIALS Joseph Anton Talalay, Boston, Mass.

SPONGY ARTICLE Application July 1, 1941, Serial No. 400,654

In Great Britain February 19, 1940 Claims.

This invention relates to the production of,

porous or'spongy articles, which may -or may not contain fibrous material reinforcement, by any method involving expansion of a fluid bearing rubber or rubber-like material into a froth, more particularly by means of pressure reduct on, with subsequent setting of the froth produced followed by vulcanisation.

The froth produced by expanding a fluid bearing rubber .or rubber-like material exhibits on gelling a contraction tendency which leads to internal strains being set up within the structure. These not only distort the structure but are manifestly detrimental in themselves, since they lead to internal rupture of the cell'or pore walls. Further, when the frothing has been effected by pressure reduction, the restoration of pressure after gelling has occurred assists these contracting forces with the result that the artic1e,-which in its set state is still soft and yielding, becomes misshapen, having, for example, some or all of its faces, and especially its lateral faces, concave in form, so that wastage is incurred in trimming the structure to a neat shape. In addition the cells of the froth become flattened under the various forces acting, which deprives the resulting sponge of its full measure of resiliency.

These drawbacks are wholly, or substantially, eliminated by the method provided by the present invention which consists in causing the froth of rubber or rubber-like material which has been expanded, to contract in a container at least one wall of which is free to move within limits in the direction of contraction of the setting froth.

' the box.

In carrying out the invention the container used may be one of which one or more or all the walls including the lid, can move in'the said manner, such a container being formed for example by securing fabric, or other flexible porous'materiai, to a wire or other frame so thatthe wall or walls is or are formed of loosely sagging fabric. Porous material permits escape of the air displaced by the expansion of the froth in the container whilst at the same time preventing escape of the froth. 1

Usually it will be sufficient to have only one wall capable of so floating, and that wall will usually most conveniently be the lid of the container. The floating wall (or lid) is conveniently a piece of loosely sagging flexible porous material, such as fabric or canvas, firmly cured at its edgesfi. e., to the neighbouring walls, by for example clamping, nailing or sticking with an adhesive, such as latex. Porous material employed as a floating wall is preferably impregnated with a coagulating agent, such as ammonium nitrate, in order to enhance it impermeability with respect to the froth.

In the accompanying drawing Figures 1 and 2 illustrate in sectional elevation, and by way of example, two forms of apparatus for carrying the invention into effect.

Referring to Figure 1, the container consists of a box a, e. g., of wood, provided with an outer lid b. A sheet of fabric 0 is fixed to'the edges I of the box on which the outer lid hears (it may be stuck to these edges, for example, or held frictionally in position by pressure of the outer lid thereon) and sags loosely in the interior of From the outer lid is suspended by means of bolts d passing loosely through holes e therein and fitted with stop nuts 1 a perforated inner plate 9 of loose sliding fit in the interior of the box. This perforated inner plate may hang freely within the fabric hammock, the said stop nuts bearing on the outer lid, or rest on the upper surface of the fabric hammock, forming therewith the inner floating" lid. The plate g and the fabr c 0 are in any case with advantage secured together, e. g., by sticking or stitching. The position of the stop nuts I on the bolts and/or the amount of sag of the hammock will limit the extent to which the inner lid may descend within the container. If desired the relative positions of, the fabric c and the-perforated plate 9 may be reversed, the latter being disposed underneath the fabric layer. A gasket 71. of gas-porous material is preferably disposed between the outer lid b and a sealing gasket-i in order to provide additional opportunity for removal of air from the interior of the box. Preferably an upright closable inlet tube 1 for introducing the fluid to be frothed, is fitted to the inner plate 0, passing with sliding fit through an aperture in the outer lid, the latter being held secure in the closed position by clamping means In. I

when theexpanding froth comes into contact with the loose movable wall, constituted in the above example by the fabric 0 and the perforated plate y, it pushes it out to a maximum extent. Then, on gelling, the contracting forces set up are equalised by the movable wall retracting under the action thereof to the extent determined by the adjustment of the stop nuts I, and a product results which is substantially free from the drawbacks mentioned above. 'It requires little or no trimming,thus reducing or eliminating waste, the pores are not flattened.

thus maintaining a high standard of resiliency for the product and, further, it is wholly or sub-' it in a plane, thus forming a movable closure for the container.

The method of the present invention may be adopted with any mode of frothing, but preferably the frothing is eflected by means of relative pressure reduction, e. g., application of a subatmospheric pressure. The container may of course also contain fibrous material, either bonded or not, so that the same is incorporated in the flnal product. Further, the frothing may be effected in one container and the setting involving the contraction, in another container, it being essential that the latter be constructed according to the present invention.

What I claim is:

- 1. An apparatus as claimed in claim 7 in which the movable wall forms an inner floating lid within the container which floating lid comprises a perforated plate and a loosely sag ing sheet of flexible porous material in contact with the said perforated plate in combination with an outer perforated lid secured to the container above the floating lid, bolts secured to the perforated plate of the inner floating lid and guiding slots in the outer perforated lid for the passage of the said bolts.

2. An apparatus asclaimed in claim 7 in which the movable wall forms an inner floating lid within the container which floating lid comprises a perforated plate and a loosely sagging sheet of flexible porous material in contact with the said perforated plate incombination with an outer perforated lid secured to the container above the floating lid. bolts secured to the perforated plate of the inner floating lid and guiding slots in the outer perforated lid for the passage of the said bolts, and stop nuts on the bolts outside the container for limiting the movement of the inner floating lid in the direction of contraction of the setting froth.

3. An apparatus as claimed in claim 7 in which the movable wall consists of an inner floating lid within the container, the latter further comtube for; the introduction of the fluid to be frothed attached to the inner floating lid. the outer perforated lid having an aperture forming a sliding flt with the said inlet tube.

4. An apparatus as claimed in claim 'I in which the movable wall consists of an inner floating lid comprising a sagging sheet of flexible porous material and of a wire frame or ring attached to the said sheet of flexible porous material.

5. The apparatus of claim 7. wherein said stretchingand holding means comprises a perforated plate combined with said flexible material.

6. The apparatus of claim 7 wherein said stretching and holding means comprises a ring member combined with said flexible material and having a shape conforming substantially to the body of the movable wall of said container.

"1. An apparatus for making porous or spongy articles of rubber or rubber-like material, from a froth of such materials, comprising a container impermeable to the froth and having side walls, a bottom wall, and a top wall, at least one of said walls having a body portion freely movable relatively to, the others, and being formed of flexible gas-permeable material, the edges of said flexible material being securely sealed to the adiacent walls of the container. and the seal being maintained during movement of the body of such wall, and means cooperating with the latter for stretching and holding said body in a plane.

8. An apparatus as claimed in claim '7, including an outer perforated plate engaging the edges of said flexible material, the sealing means comprising a gasket of gas-permeable material disposed between said perforated plate and certain edges of said container.

9. An apparatus as claimed in claim 7, including an outer perforated plate arranged parallel impermeable to the froth and having side walls,

a bottom wall, and a top wall, the top wall having a body portion freely movable relatively to the others and said top wall being formed of flexible gas-permeable material, the edges of said prising an outer perforated lid. a closable inlet flexible material being sealed to the adjacent walls of the container, the seal being maintained during movement of said body, and means for holding the body portion of said top wall in stretched condition.

' JOSEPH ANTON TALALAY. 

